#include <cstdio>
#include <cstring>
#include <iostream>
#include <unistd.h>

int main() {
    // 库函数
    printf("hello world\n");
    fprintf(stdout, "hello fprintf\n");
    const char* s = "hello fwrite\n";
    fwrite(s, strlen(s), 1, stdout);

    // 系统调用
    const char* ss = "hello write\n";
    write(1, ss, strlen(ss));

    // c++的几个输出
    std::cout << "hello cout" << std::endl;
    std::cerr << "hello cerr" << std::endl;
    return 0;
}